Ideas for porting an MS361

[huskihl]

I'm resurrecting a crushed MS361. This 361 was part of a labor trade I made awhile back. I checked out one of Stumpy's threads and noticed this saw may not respond as well to typical porting modifications as others. I'm thinking widening/ squaring the exhaust and intake, as there's lots of room to do this, matching the lowers to the piston skirts, adding a larger carb, and gutting the muffler/adding a 2nd port.

Any tips / do's / don'ts that I might look for or stay away from?

 

[Terry Syd]

I always thought the 361 would be a neat saw to mod. I like a strong, lightweight saw so I would tend to emphasize those aspects of an already great saw. If it was mine, I'd probably port an aftermarket 64cc jug, MM, a modded bigger carb and manifold, probably bigger air filter then put a 20" NK bar on it - and end up with an even stronger and lighter saw.

If I ever find a toasted one here in Oz, that would be my plan.

There should be a few fellows on the forum that have some more practical ideas.

 

[mdavlee]

Bump the compression with a little machine work or do a gasket delete. Numbers wise I don't know stock to say how I would change it.

 

[huskihl]

Bump the compression with a little machine work or do a gasket delete. Numbers wise I don't know stock to say how I would change it.

Stock #'s without gasket are e 104, t 132, and I think intake was 74

 

[mdavlee]

Lots of blowdown on it. I would think shortening the blow down would make a better running saw.

 

[huskihl]

Lots of blowdown on it. I would think shortening the blow down would make a better running saw.

Yea. Then I think 7900 too

 

[mdavlee]

7900 likes 28-30

 

[huskihl]

7900 likes 28-30

Yep. I didn't wanna raise them more than they were originally because of the dolmar stories. The 361 is a quad with wide intake transfers already, with an 1/8" bottleneck in the runners up inside

 

[huskihl]

Top ring is dead center intake, bottom ring is on exhaust skirt

 

[mdavlee]

Have to see pictures but it's probably done for velocity

 

[drf256]

This will be an interesting thread.

The only quad I've ever done is the little echo 490, and it's at 16* BD with plenty of grunt.

Is the case really tight like a Dolly?

I'd say anything you remove with increase case volume and you'd need higher transfers. Because it's case fed transfers, you'll be decreasing case volume when you cut the base.

Any pics of the victim?

 

[drf256]

I have on of Brads 361's here. Never ran it. I know it's a single ring popup saw.

I've heard his 361's are quite stout. I'll likely bring it to the CT GTG.

You may wanna do some AS research on what he's done. You may wanna try a popup.

What was the squish with no gasket?

 

[drf256]

Found this thread on the AS.

http://www.arboristsite.com/community/threads/project-stumpbroke-ms361.221405/#post-4076723

Maybe someone can find Stumpy?

He doesn't mention numbers. By the looks of the jug, he did raise the transfers.

 

[David Young]

ditch the bottom ring the transfer number can come up a bunch but always make small changes if you don't know. Compression always helps, where is your compression now?

 

[drf256]

Brad clocked a stock 361 at 168 psi in one of his old threads from 2008.

 

[huskihl]

Thanks for the replies guys. Squish without the gasket was tightest at the perimeter at .014. Compression is 170. The 30° of blow down really threw me for a loop. I read Stumpy's thread. Tlandrum ended at 20° bd and Timber Wolf ended at 23°. Biggest difference was exhaust height. Terry was at I think 101, and TW at 97. I'll do some safe grinding on it and will start testing at e 103, Trans 128 and see how it goes from there

 

[Miller Mod Saws]

103/123/? I can't remember intake I'd haft to look at my notes. I think I take .040 or .050" off my base. Again I can look when I get home. But iirc I liked 20 blowdown! And I think 78 intake but it's been awhile.

 

[huskihl]

103/123/? I can't remember intake I'd haft to look at my notes. I think I take .040 or .050" off my base. Again I can look when I get home. But iirc I liked 20 blowdown! And I think 78 intake but it's been awhile.

Those #s are lIke others I've seen, Carl. Usually when I see 27° bd the first time on the degree wheel I think 7900 and start to flinch wondering if I should raise to 20° bd or not

 

[David Young]

open up the muffler and start a little higher on the transfers.

I really like what carl suggested but I haven't built one and wouldn't suggest it off the bat.

 

[WOODS]

I don't know a thing about porting except my WWS 361 rips. Whatever recipe Terry Landrum used was right. Ron